Mr Swaay you are exactly right i have the same symptoms on my w124 1991 300 D 2.5 Turbo Diesel project car the transmission was working flawlessly till one day in a cold run i stopped at the red light and no more forward movement since. I opened the tranny fluid pan (fluid was in very nice shape no weird colors or residue or metallic parts nor smell) and in it i found the dogbone reaction valve pin floating and the plastic seal that covers it broken. By reading through countless post here about the B2 piston and the brake band i am 100 % sure that this is the part that is causing my problem i went to MB dealership and ordered the plastic part, a rubber gasket/seal and the reaction valve from whole sale parts for $40 something dollars now how do you replace it is there a way to reaplace the reaction valve of the b2 piston without completely removing the transmission??? I know you can remove the actual B2 piston but how about getting to this reaction valve can you get to it though the B2 hole/?? from reading through the posts i understand that the brake band is in the middle and around the center of the transmission right?? and than this reaction valve on the driver side and the B2 on the passenger side. Can you get to the reaction valve from the driver side some how??? how about removing the 10 screws visible from underneath the transmission valve cover that sits in oil ?? if you remove those can this valve be accessed or not really?? please help if i can get this myself without dropping the whole transmission i might tackle it but if i have to remove the whole tranny than i will take it somewhere
thanks again for the help
denis